FMF - Friends of Minerals Forum, discussion and message board

[rockbottom]

Does anyone know how or if there is a test to confirm the presence of Platinum? Thanks for your time!

[Pete Modreski]

There are some chemical tests, but I think they are a bit involved and would require some special test chemicals that most people would not have access to. That's about as much as I know offhand, without trying to look up exactly what such tests are.
---Pete

P.S., referring back to the earlier thread on this Forum about supposed palladium-bearing gold ( https://www.mineral-forum.com/message-board/viewtopic.php?t=401 ) some who are on this list and are also MSA members, may have read the posts on the MSA's listserv by Jacques Jedwab (Brussels), who has web pages dealing with "Unconventional platinum-group minerals and mineraloids". These are a variety of poorly or non-crystalline oxide and other compounds associated with gold or platinum-bearing grains and nuggets, and which he proposes to call "Antonil compounds",

"...in recognition of Padre Antonil, who was the first to describe in print the black auriferous mineral grains found around 1695-1700 in Minas Gerais, Brazil, and known since then as “ouro preto” (Pt was to be discovered 50 years later, and Pd 100 years). "

His main web pages are at,
https://www.ulb.ac.be/sciences/upgm/mguide/
and include a comprehensive list of the reported occurrences of such minerals and mineraloids. His article about this that was published in Canadian Mineralogist in 1998,
https://canmin.geoscienceworld.org/cgi/content/abstract/36/3/887
(I think you will not be able to access the text of this, without a subscription) contains a good and interesting historical review of the discovery and puzzlement over, these various minerals.

I thought some of this might be of interest to some on Jordi's forum.

Pete Modreski

[keldjarn]

Platinum nuggets can probably be identified without sofisticated equipment by physical properties i.e. the very high density. In most cases platinum or other PGMs will be present in small amounts disseminated in rock- and ore samples (or as minute grains in placer deposits). In such cases there are commercial assay laboratories with a lot of experience in the detection of these valuable elements using i.e. ICP ( Coupled plasma emission spectrometer ). You will easily find references to such labs on the internet.
Knut

[Angie]

Hi, I'm one of the uninitiated of the mineral world. I recently found a couple of small rocks while metal detecting. One at the beach, the other in my backyard. (Melbourne, Australia) I'm new to metal detecting and took a closer look at these rocks that registered a distinct beep.
I've done a couple of basic tests, streak and hardness. Both have a grey streak with a metallic glint. Both pass the fingernail test but scratch with copper coin.
I only have old kitchen scales that don't cater for such small weights but I'm guessing the one found in the sand at the beach is about 5g and the second 7g.

Do they look like platinium, palladium, silver or Rhodium ? I really would appreciate any help in identifying these small finds.

[Angie]

I should mention the samples were wet in sugar water (advised in another thread for photos) in the hope that it would bring out the various surface features.
The first backyard photo shows the scratch test revealing the metallic shine.

[alfredo]

Try taking a photo without the sugar water. The sugar water advice was for transparent crystals with inclusions, not for metallic minerals. For metallic minerals it actually ruins our ability to tell what it is ;-((

[Angie]

Thanks Alfredo.
I thought it might help as some of the finer surrounding grains are hard to see when dry. I'll try tomorrow as it's rather late here.

[Pete Richards]

According to my textbook, platinum has a hardness of 4 to 4 1/2. I don't know how consistent the hardness is of copper coins made in different countries, but in the U.S. a copper penny is supposed to have a hardness of 3. So I suspect platinum should not be scratched by a copper coin. One unhappy possibility is that what you have is lead. I remember as a student panning some gold and a silver-grey metal from glacial sand in a local stream. I was quite let down when I found out that my "platinum" was actually lead, presumably fragments of bullets or fishing sinkers.

If you have access to acids and a place to use them safely, lead will dissolve in nitric acid. And if I'm not mistaken, it will develop a white coating when placed in dilute hydrochloric (muriatic) acid. Maybe someone else will confirm this.

[Angie]

Thaaanks Pete! I must admit the more I try searching the various sites for streak colour clues and hardness levels, the more I get confused. Hardness varies on composition % 's as most are not found pure. Lead varies from 1,5 to 2.5 fingernail, but I can't scratch either with my fingernail. The only lead sinker I can find at the moment looks like it has a protective coating. It has a similar streak colour but not as uniform in line...if that makes any sense. I checked to see how the two finds and the lead sinker compared in conductivity on the metal detector. The beach find was lowest (under section for gold and pull tabs), then the lead sinker and the backyard find only slightly higher ( nearer the section for silver) than the lead sinker. Any way, here are the photos, dry!